Inspection position identification method, three-dimensional image generation method, and inspection device

ABSTRACT

An inspection position identification method that allows accurate inspection to be performed without in-advance identification of the position of an inspection plane in an inspected target. A three-dimensional image generation method that allows generation of a three-dimensional image for inspection without in-advance identification of the position of an inspection plane in an inspected target and then allows inspection to be performed. An inspection device including the methods. An inspection device includes a storage unit, which stores a radiation transmission image of an inspected object and a three-dimensional image generated from the radiation transmission image, and a control unit. The process carried out by the control unit for identifying an inspection position in a three-dimensional image includes identifying the position of a transmission picture of the inspection position in the radiation transmission image and identifying the inspection position in the three-dimensional image from the position of the transmission picture.

The present application is a continuation of U.S. patent applicationSer. No. 16/652,016 filed on Mar. 27, 2020, which is a National Phase ofInternational Application No. PCT/JP2018/035606, filed Sep. 26, 2018,and claims priority based on Japanese Patent Application No.2017-187450, filed Sep. 28, 2017 and Japanese Patent Application No.2017-187451, filed Sep. 28, 2017. The contents of the above applicationsare incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to an inspection position identificationmethod in inspecting an inspected object, a three-dimensional imagegeneration method, and an inspection device including the methods.

BACKGROUND ART

As an inspection device that measures the shape of solder on top andbottom surfaces of a substrate, there is an X-ray inspection devicebased on tomosynthesis (see Patent Literature 1, for example).

CITATION LIST Patent Literature

Patent Literature 1: Japanese Patent Laid-Open No. 2008-026334

SUMMARY OF INVENTION Technical Problem

However, such an X-ray inspection device needs to identify the positionsof the top and bottom surfaces of the substrate in a Z direction (X-rayprojection direction or height direction with respect to top surface ofsubstrate), for example, with a laser length measurer in advance andreconstruct a tomographic image at the height or extract an optimumZ-direction image out of the reconstructed tomographic image, resultingin a problem of a long inspection period.

The present invention has been made in view of the problem describedabove, and an object is to provide an inspection position identificationmethod that allows accurate inspection to be performed withoutin-advance identification of the position of an inspection plane(Z-direction position) in an inspected target, a three-dimensional imagegeneration method that allows generation of a three-dimensional imagenecessary for inspection without in-advance identification of theposition of an inspection plane (Z-direction position) in an inspectedtarget and then allows inspection to be performed, and an inspectiondevice including the methods.

Solution to Problem

To solve the problem, an inspection position identification methodaccording to a first present invention is an inspection positionidentification method for identifying an inspection position in athree-dimensional image generated from a radiation transmission image ofan inspected object, the method being characterized by including: a stepof identifying a position of a transmission picture of the inspectionposition in the radiation transmission image; and a step of identifyingthe inspection position in the three-dimensional image from the positionof the transmission picture.

In this sort of inspection position identification method according tothe present invention, the step of identifying the position of atransmission picture preferably performs the identification by using ashape of a transmission picture of a specific pattern or mark in theinspection position or in a vicinity of the inspection position.

An inspection device according to the present invention is characterizedby including: a storage unit that stores the radiation transmissionimage and the three-dimensional image; and a control unit that extractsthe radiation transmission image from the storage unit and identifiesthe inspection position in the three-dimensional image by using theinspection position identification method described above.

A three-dimensional image generation method according to a secondpresent invention is a three-dimensional image generation method forgenerating a three-dimensional image of an inspected object from aradiation transmission image of the inspected object, the method beingcharacterized by including: a step of identifying a position of atransmission picture of an inspection position in the inspected objectin the radiation transmission image; a step of identifying theinspection position in the three-dimensional image from the position ofthe transmission picture; and a step of generating a three-dimensionalimage of the inspected object containing the inspection position fromthe radiation transmission image.

In the three-dimensional image generation method according to thepresent invention, the step of identifying the position of atransmission picture preferably performs the identification by using ashape of a transmission picture of a specific pattern or mark in theinspection position or in a vicinity of the inspection position.

An inspection device according to the present invention is characterizedby including: a storage unit that stores the radiation transmissionimage and the three-dimensional image; and a control unit that extractsthe radiation transmission image from the storage unit and generates athree-dimensional image of the inspected object by using thethree-dimensional image generation method described above.

Advantageous Effect of Invention

The inspection position identification method according to the presentinvention allows accurate inspection to be performed without in-advanceidentification of the position of an inspection plane (Z-directionposition) in an inspected target.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a descriptive diagram showing the configuration of aninspection device according to an embodiment.

FIG. 2 is a descriptive diagram of each functional block processed by acontrol unit of the inspection device.

FIG. 3 is a flowchart for describing the procedure of inspection.

FIG. 4 is a descriptive diagram showing the amount of correction in areconstructed space.

FIGS. 5A and 5B are descriptive diagrams showing a substrate inspectionplane identification method. FIG. 5A shows the method in a firstembodiment, and FIG. 5B shows the method in a second embodiment.

FIGS. 6A and 6B are descriptive diagrams for describing a method fordetermining a position in a reconstructed image from two transmissionimages.

FIG. 7 is a descriptive diagram showing a substrate inspection planeidentification method in a third embodiment.

FIG. 8 is a flowchart for describing the procedure of inspection in thethird embodiment.

DESCRIPTION OF EMBODIMENT

A preferred embodiment of the present invention will be described belowwith reference to the drawings. An inspection device 100 according tothe present embodiment is configured by including a control unit 10constituted by a processing device such as a PC, a monitor 12, and animaging unit 32, as shown in FIG. 1. The imaging unit 32 furtherincludes a radiation quality modification unit 14, a radiation generatordrive unit 16, a substrate holding unit drive unit 18, a detector driveunit 20, a radiation generator 22, a substrate holding unit 24, and adetector 26.

The radiation generator 22 is a device that generates radiation such asX rays. For example, the radiation generator 22 generates radiation bycausing accelerated electrons to collide with a target such as tungstenor diamond.

The substrate holding unit 24 holds a substrate that is an inspectedobject. The substrate held by the substrate holding unit 24 isirradiated with the radiation generated by the radiation generator 22,and the detector 26 captures an image of the radiation having passedthrough the substrate. A radiation transmission image of the substratecaptured with the detector 26 is hereinafter referred to as a“transmission image.” In the present embodiment, the substrate holdingunit 24 holding the substrate and the detector 26 are moved relative tothe radiation generator 22, and a plurality of transmission images areacquired to generate a reconstructed image.

The transmission images captured with the detector 26 are sent to thecontrol unit 10, and a known technology such as afiltered-backprojection method (FBP method), is used to reconstruct thetransmission images into an image containing the stereoscopic shape ofsolder at a bonded portion. The reconstructed image and the transmissionimages are stored in a storage in the control unit 10 or an externalstorage that is not shown. A reconstructed three-dimensional imagecontaining the stereoscopic shape of solder at a bonded portion based onthe transmission images is hereinafter referred to as a “reconstructedimage.” An image cut from the reconstructed image and showing anarbitrary cross-section is referred to as a “tomographic image.” Thethus generated reconstructed image and tomographic image are output tothe monitor 12. The monitor 12 displays not only the reconstructed imageand the tomographic image but, for example, the result of inspection ofthe solder bonding state, which will be described later. Thereconstructed image in the present embodiment is also referred to as a“planar CT” because it is reconstructed from planar images captured withthe detector 26, as described above.

The radiation quality modification unit 14 modifies the quality of theradiation generated by the radiation generator 22. The quality of theradiation is determined by the voltage applied to accelerate theelectrons to be caused to collide with the target (hereinafter referredto as “tube voltage”) and current that determines the number ofelectrons (hereinafter referred to as “tube current”). The radiationquality modification unit 14 is a device that controls the tube voltageand the tube current. The radiation quality modification unit 14 can beimplemented by using known technologies such as a transformer and arectifier.

The quality of the radiation is determined by the luminance and hardnessof the radiation (spectral distribution of radiation). Increasing thetube current increases the number of electrons that collide with thetarget and therefore increases the number of photons in the generatedradiation. As a result, the luminance of the radiation increases. Forexample, some components, such as capacitors, are thicker than the othercomponents and need to be irradiated with high luminance radiation forcapture of transmission images of the thicker components. In this case,the tube current is adjusted to adjust the luminance of the radiation.Increasing the tube voltage increases the energy of the electrons thatcollide with the target and therefore increases the energy (spectrum) ofthe generated radiation. In general, the greater the energy of theradiation, the greater the penetration force of the radiation to theobject, and the harder it is for the radiation to be absorbed by theobject. Transmission images captured by using such radiation have lowcontrast. The tube voltage can therefore be used to adjust the contrastof the transmission images.

The radiation generator drive unit 16 includes a drive mechanism that isnot shown, such as a motor, and can move the radiation generator 22upward and downward along the axis passing through the focal point ofthe radiation generator 22. It is therefore possible to change thedistance between the radiation generator 22 and the inspected object(substrate) held by the substrate holding unit 24 to change theirradiation field, whereby the magnification of the transmission imagescaptured with the detector 26 can be changed.

The detector drive unit 20 also includes a drive mechanism that is notshown, such as a motor, which rotates the detector 26 to move along adetector rotation trajectory 30. The substrate holding unit drive unit18 also includes a drive mechanism that is not shown, such as a motor,and translates the substrate holding unit 24 along a flat plane in whicha substrate rotation trajectory 28 is provided. The substrate holdingunit 24 is configured to rotate to move along the substrate rotationtrajectory 28 in conjunction with the rotating motion of the detector26. A plurality of transmission images can thus be captured alongdifferent projection directions and at different projection angles withthe relative positional relationship between the substrate held by thesubstrate holding unit 24 and the radiation generator 22 changed.

The turning radius of each of the substrate rotation trajectory 28 andthe detector rotation trajectory 30 is not fixed but can be freelychanged. The irradiation angle at which a component disposed on thesubstrate is irradiated with the radiation can therefore be arbitrarilychanged.

The control unit 10 controls the entire operation of the inspectiondevice 100 described above. A variety of functions of the control unit10 will be described below with reference to FIG. 2. Although not shown,an input device, such as a keyboard and a mouse, is connected to thecontrol unit 10.

The control unit 10 includes a storage unit 34, a tomographic imagegeneration unit 36, a substrate inspection plane detection unit 38, apseudo-tomographic image generation unit 40, and an inspection unit 42.Although not shown, the control unit 10 further includes an imagingcontrol unit that controls the radiation quality modification unit 14,the radiation generator drive unit 16, the substrate holding unit driveunit 18, and the detector drive unit 20. Each of these functional blocksmay be implemented by cooperation between hardware, such as a CPU thatperforms a variety of types of computation processing and a RAM used asa work area for data storage and program execution, and software. Thefunctional blocks can therefore be implemented in a variety of formsbased on the combination of the hardware and the software.

The storage unit 34 stores imaging conditions for capturing transmissionimages of the substrate, design information and the like of thesubstrate, which is the inspected object, and other pieces ofinformation. The storage unit 34 further stores the transmission imagesand a reconstructed image (tomographic image and pseudo-tomographicimage) of the substrate, the result of inspection performed by theinspection unit 42, which will be described later, and the like. Thestorage unit 34 still further stores the speed at which the radiationgenerator drive unit 16 drives the radiation generator 22, the speed atwhich the substrate holding unit drive unit 18 drives the substrateholding unit 24, and the speed at which the detector drive unit 20drives the detector 26.

The tomographic image generation unit 36 generates tomographic imagesbased on a plurality of transmission images acquired from the storageunit 34. This can be implemented by using a known technology, forexample, the FBP method and a maximum likelihood method. Differentreconstruction algorithms cause different characteristics of theresulting reconstructed images and different periods required for thereconstruction. In view of the fact described above, a configuration maybe adopted in which a plurality of reconstruction algorithms andparameters used in the algorisms may be prepared in advance, and a usermay select any of the prepared reconstruction algorithms and parameters.Thereby, priority can be given to reduction in the period necessary forthe reconstruction or priority to improvement in the image quality atthe sacrifice of a long period, that is, the user can thus be providedwith selection flexibility. A generated tomographic image is output tothe storage unit 34 and recorded in the storage unit 34.

The substrate inspection plane detection unit 38 identifies the position(tomographic image) of a displayed inspection target plane of thesubstrate (top surface of substrate, for example) out of the pluralityof tomographic images generated by the tomographic image generation unit36. The tomographic image that displays the inspection plane of thesubstrate is hereinafter referred to as an “inspection plane image.” Aninspection plane image detection method will be described later indetail.

The pseudo-tomographic image generation unit 40 stacks a predeterminednumber of continuous tomographic images out of the tomographic imagesgenerated by the tomographic image generation unit 36 to visualize asubstrate area thicker than each tomographic image. The number ofstacked tomographic images is determined by the thickness of thesubstrate area displayed by the tomographic images (hereinafter referredto as “slice thickness”) and the slice thickness of thepseudo-tomographic image. For example, when the slice thickness of eachtomographic image is 50 μm, and the height of a BGA solder ball(hereinafter simply referred to as “solder”) (500 μm, for example) isset as the slice thickness of the pseudo-tomographic image, 500/50=10tomographic images may be stacked. In this process, the inspection planeimage identified by the substrate inspection plane detection unit 38 isused to identify the position of the solder.

The inspection unit 42 inspects the solder bonding state based on thetomographic images generated by the tomographic image generation unit36, the inspection plane image identified by the substrate inspectionplane detection unit 38, and the pseudo-tomographic image generated bythe pseudo-tomographic image generation unit 40. Since the solder thatbonds a component to the substrate is located in the vicinity of thesubstrate inspection plane, inspecting the inspection plane image andtomographic images that display an area on a side of the inspectionplane image that is the side facing the radiation generator 22 allowsevaluation of whether the solder has appropriately bonded the componentto the substrate.

The term “solder bonding state” means whether the solder has bonded thecomponent to the substrate in such a way that an appropriateelectrically conductive path is generated. Inspection of the solderbonding state includes bridge inspection, melted state inspection, andvoid inspection. The term “bridge” means a non-preferableinter-conductor electrically conductive path generated by the solderbonding. The term “melted state” means a state in which the bondingbetween the substrate and the component is insufficient or not due toinsufficient solder melting or a state in which what is called“floating” has occurred or not. The term “void” means solder bondingfailure due to air bubbles in the solder bonded portion. The inspectionunit 42 therefore includes a bridge inspection unit 44, a melted stateinspection unit 46, and a void inspection unit 48.

The operation of each of the bridge inspection unit 44, the melted stateinspection unit 46, and the void inspection unit 48 will be describedlater in detail. The bridge inspection unit 44 and the void inspectionunit 48 inspect bridges and voids, respectively, based on thepseudo-tomographic image generated by the pseudo-tomographic imagegeneration unit 40, and the melted state inspection unit 46 inspects thesolder melted state based on the inspection plane image identified bythe substrate inspection plane detection unit 38. The results of theinspection performed by the bridge inspection unit 44, the melted stateinspection unit 46, and the void inspection unit 48 are recorded in thestorage unit 34.

FIG. 3 is a flowchart showing the procedure from the capture oftransmission images, the generation of a reconstructed image, and theidentification of an inspection plane image to the inspection of thesolder bonding state. The processes in the present flowchart start, forexample, when the control unit 10 accepts an inspection startinstruction from an input device that is not shown.

The control unit 10 causes the radiation generator drive unit 16 to seta field irradiated with the radiation radiated by the radiationgenerator 22, causes the substrate holding unit drive unit 18 to movethe substrate holding unit 24, causes the detector drive unit 20 to movethe detector 26 to change the imaging position, causes the radiationquality modification unit 14 to set the quality of the radiation fromthe radiation generator 22, causes the radiation generator 22 to radiatethe radiation to the substrate, causes the detector 26 to capturetransmitted images, and further causes the tomographic image generationunit 36 and the pseudo-tomographic image generation unit 40 to generatea reconstructed image from the plurality of thus captured transmissionimages (step S10).

The substrate inspection plane detection unit 38 in the control unit 10then receives the transmitted images or the reconstructed image(tomographic images) from the tomographic image generation unit 36 andidentifies an inspection plane image from the received images (stepS12). The bridge inspection unit 44 acquires a pseudo-tomographic imagedisplaying a solder ball and having a slice thickness roughly equal tothe height of the solder ball from the pseudo-tomographic imagegeneration unit 40 and inspects the presence or absence of bridge (stepS14). In a case where no bridge has been detected (“N” in step S16), themelted state inspection unit 46 acquires the inspection plane image fromthe substrate inspection plane detection unit 38 and inspects whetherthe solder has been melted (step S18). When the solder has been melted(“Y” in step S20), the void inspection unit 48 acquires apseudo-tomographic image partially displaying the solder ball from thepseudo-tomographic image generation unit 40 and inspects whether a voidis present (step S22). When no void is found (“N” in step S24), the voidinspection unit 48 determines that the solder bonding state is normal(step S26) and outputs the result of the evaluation to the storage unit34. When a bridge is found (“Y” in step S16), the solder has not melted(“N” in step S20), and a void is present (“Y” in step S24), the bridgeinspection unit 44, the melted state inspection unit 46, and the voidinspection unit 48 determine that the solder bonding state is abnormal(step S28) and outputs the result of the evaluation to the storage unit34. When the state of the solder is output to the storage unit 34, theprocesses in the present flowchart are terminated.

As described above, a reconstructed image (reconstructed space), whichis a three-dimensional image reconstructed from transmission images,contains image data on the substrate having errors resulting from, forexample, inclination, shift, bending, rotation, and expansion/shrinkage.Therefore, to perform automatic inspection, it is necessary to performposition correction in consideration of the errors and identify aninspection plane image based on the position correction. An inspectionposition (substrate inspection plane) identification method (errorcorrection method) in the substrate inspection plane detection processS12 will be described below.

First Embodiment

A first embodiment of the inspection position identification method willbe described below. In the aforementioned generation of a reconstructedimage (step S10), planar CT computation is performed over a wide rangecontaining the top and bottom surfaces of the substrate (range inconsideration of errors, such as aforementioned warpage of substrate) toacquire a three-dimensional image (reconstructed image) containing theerrors, such as warpage of the substrate, and information on substratedesign is used to detect, from the three-dimensional image(reconstructed image), the shape of a specific pattern or mark (image ofspecific pattern or mark) for identifying the inspection position in X,Y, and Z directions over a plurality of tomographic images. Thesubstrate inspection plane (inspection plane image) is thus determined.

The term “information on substrate design” refers to Gerber data and CAD(computer aided design) data and are stored in advance in the storageunit 34 described above. Recorded information on the coordinates of thesolder bonded portion is called the Gerber data, and information on thetype of a mounted component and the coordinates of the mounted positionrecorded in the storage unit 34 is called the CAD data. The coordinatesof the solder bonded portion and the component mounted position areexpressed as the coordinates in an X and Y coordinate system set on thesubstrate. Referring to the Gerber data and the CAD data and performingimage matching (pattern matching) or any other processing on thereconstructed image (tomographic images) allow the type and size of thecomponent present on the substrate and the positions of the componentand the solder bonded portion to be obtained, that is, the inspectionposition (inspection plane image) to be identified.

Specifically, a substrate surface image that serves as a template isregistered for each of the top and bottom surfaces of the substrate forthe field of view (FOV) of each transmission image or for each of 4areas of the FOV that are 2×2=4 divided areas thereof (Gerber data andCAD data described above can be used). Image matching is then performedby using the registered template in a predetermined XYZ search range onan FOV basis of each substrate under imaging, and a position wherehighest coincidence is achieved is used as the amount of shift.Detection of the amount of shift for each FOV or for each of the 4divided areas of the FOV allows one or four amounts of shift in one FOVto be obtained, and the amounts of shift are each expressed as thevertex of a triangle over the entire substrate, as shown in FIG. 4. Toperform an inspection the area surrounded by each of the triangles, theamount of correction is calculated from the amount of shift expressed bythe vertex of the triangle (amount of shift from reference surface iscalculated), and an inspection plane image is determined based on theamount of correction. Using the amount of shift expressed by the vertexof a triangle allows correction of the shift in the X, Y, and Zdirections and correction of the rotation around the X, Y, and Z axes.When there are a plurality of inspection locations, tomographic imagesare determined from the errors described above in accordance with eachinspection location, and the determined tomographic images are used togenerate a pseudo-tomographic image, followed by inspection, and thesame processes are carried out at the following inspection location. Foran inspection target component that requires further high-precisionposition correction, the position correction is performed individually.In this case, the surfaces of the substrate have been roughly detectedin advance by the image matching, whereby the processes can be carriedout over a limited search range and therefore at high speed.

Second Embodiment

In the inspection position (substrate inspection plane) identificationmethod according to the first embodiment, a three-dimensional image(reconstructed image) over a range in consideration of the errors, suchas warpage of the substrate, is reconstructed from transmission images,and the three-dimensional image is used to identify the inspectionposition, as shown in FIG. 5A. In contrast, in the inspection position(substrate inspection plane) identification method according to a secondembodiment, the shape of an image of a specific pattern or mark(transmission pictures) IA1 and IA2 is detected in two or moretransmission images, and the position of the shape of the specificpattern or mark (image of specific pattern or mark in three-dimensionalimage) A in the three-dimensional image (reconstructed image) isidentified based on the X, Y, and Z positions of the transmissionpictures in each of the transmission images to determine an inspectionplane image, as shown in FIG. 5B.

A method for identifying the position of the image A of a specificpattern or mark in a reconstructed image (position wherethree-dimensional image A of specific pattern or mark is present inreconstructed space (reconstructed image)) from the position wheretransmission pictures of the specific pattern or mark (points IA1 andIA2 in the description) have been detected in two transmission imageswill be described with reference to FIGS. 6A and 6B. In the inspectiondevice 100 according to the present embodiment, an inspection targetsubstrate (substrate holding unit 24) and the detector 26 are movedrelative to a fixed radiation source (radiation generator 22) to capturea plurality of transmission images with the radiation projection anglewith respect to the substrate changed, as shown in FIG. 1. FIG. 6A showsa case where the inspection target substrate is fixed and the radiationsource (radiation generator 22) and the detector 26 are moved. Aposition (coordinates) in FIGS. 6A and 6B can be determined incalculation by using the positions of the radiation source (radiationgenerator 22), the substrate (substrate holding unit 24), and thedetector 26 in the inspection device 100 (positions with respect topredetermined origin in inspection device 100). In FIGS. 6A and 6B, thereference position (reference point) is O.

First, the position of the radiation source at a first projection angle(coordinates representing radiation radiated from radiation generator22) is set at (SX1, SY1, SZ1), the position where the detector 26 hasdetected the transmission picture IA1 of the specific pattern or mark isset at (DX1, DY1, DZ1), and the position of the image A of the specificpattern or mark in the reconstructed image is set at (OX, OY, OZ). Theposition of the radiation source at a second projection angle is set at(SX2, SY2, SZ2), and the position of the transmission picture IA2 in thedetector 26 is set at (DX2, DY2, DZ2). OX and OY, which areX/Y-direction positions of the image A of the specific pattern or markin the reconstructed image, may be determined as points in the X and Yplanes where the straight line that connects the coordinates of theradiation source and the detector at the first projection angleintersect the straight line that connects the coordinates of theradiation source and the detector at the second projection angle, asshown in FIG. 6B and are determined by solving simultaneous equations(1) and (2) below for OX and OY.

OY=(SY1−DY1)/(SX1−DX1)·OX+(SX1·DY1−SY1·DX1)/(SX1−DX1)  (1)

OY=(SY2−DY2)/(SX2−DX2)·OX+(SX2·DY2−SY2·DX2)/(SX2−DX2)   (2)

OZ, which is the Z-direction position of the image A of the specificpattern or mark in the reconstructed image, can be determined fromExpression (3) below by using the value of OX determined by Expressions(1) and (2) described above.

OZ=(SZ1−DZ1)/(SX1−DX1)·(OX−DX1)  (3)

As described above, in the substrate inspection plane detection processS12 in the second embodiment, the inspection position in the substrate(inspection plane image in reconstructed image) is identified from theplurality of transmission images acquired in step S10. Specifically, theshape of a transmission picture of the specific pattern or mark isdetected in transmission images, for example, by using image matching,and the position of the transmission picture along with Expressionsdescribed above is used to determine the position of the pattern or markin the reconstructed image to identify an inspection plane image. Theinspection can then be performed by using the inspection plane image(tomographic image) in the accurate position. The inspection position(inspection plane image) is not identified from the entirethree-dimensional image (reconstructed image) but is identified from thetransmission images the amount of data of which is smaller than theamount of data of the reconstructed image, resulting in a decrease inthe period for the identification. As a result, the overall inspectionperiod can be shortened. In a case where there are a plurality ofinspection target locations, the shape of the specific pattern or mark(shape of transmission picture) at an inspection location or in thevicinity of the inspection location is registered, and the position ofthe shape in each of the transmission image is identified by imagematching. The position (inspection plane image) in the reconstructedimage can thus be identified.

Referring to three positions of the specific pattern or mark allowsgeneration of a pseudo-tomographic image in consideration of thepositions in the X and Y directions and the rotation around the X, Y,and Z axes instead of only the position in the Z direction and therotation around the Z direction. Further, referring to four or morepositions of the specific pattern or mark and using a knowninterpolation method, such as linear interpolation, parabolicinterpolation, and cubic interpolation, allow generation of apseudo-tomographic image in consideration of bending of the targetobject.

Third Embodiment

In the first and second embodiments, after transmission images arecaptured, a reconstructed image is generated in step S10, and thetransmission images or the reconstructed image is used to identify asubstrate inspection plane in step S12, as shown in FIG. 3. The thirdembodiment is configured such that the inspection position (substrateinspection plane) in the reconstructed space is identified from thetransmission images, and a reconstructed image containing the identifiedposition (reconstructed image containing specific pattern or mark) isreconstructed, as shown in FIG. 7.

FIG. 8 shows a flowchart for inspection of the solder bonding state inthe third embodiment, and the same processes as those described abovehave the same reference characters and detailed descriptions thereofwill be omitted. When the inspection starts, the control unit 10 causesthe radiation generator drive unit 16 to set the field irradiated withthe radiation radiated from the radiation generator 22, causes thesubstrate holding unit drive unit 18 to move the substrate holding unit24, causes the detector drive unit 20 to move the detector 26 to changethe imaging position, causes the radiation quality modification unit 14to set the quality of the radiation from the radiation generator 22,causes the radiation generator 22 to radiate the radiation to thesubstrate, and causes the detector 26 to capture transmitted images(step S11), as described above. The transmission images are then used toidentify the position of an image of the inspection target in thetransmission images, for example, by using image matching, and theposition of the image of the inspection target in the reconstructedspace (reconstructed image) is identified from the identified position(step S12), as described in the second embodiment. A reconstructed image(inspection plane image or tomographic images) containing the positionidentified in step S12 is then generated (step S13). The inspection ofthe solder bonding state by using the reconstructed image is the same asthe inspection described above (steps S14 to S28).

According to the third embodiment, in which the generation of areconstructed image is limited to a portion containing the inspectiontarget, the amount of data on the reconstructed image decreases,resulting in a decrease in the period for the generation of thereconstructed image. As a result, the overall inspection period can beshortened.

1. An inspection device that inspects an inspected substrate using a three-dimensional image generated from a radiation transmission image of the inspected substrate, the device being characterized by comprising: a radiation generator for irradiating the inspected substrate with radiation; an inspected substrate holding unit that holds the inspected substrate; a first drive mechanism for moving the inspected substrate holding unit around an axis passing through a focal point of the radiation of the radiation generator; a radiation detector for detecting the radiation having passed through the inspected substrate; a second drive mechanism for moving the radiation detector around the axis passing through the focal point of the radiation of the radiation generator; a control unit that generates a three-dimensional image from a radiation transmission image detected by the radiation detector; and an inspection area identification unit that divides a tomographic image in the three-dimensional image into a plurality of areas, calculates a piece of shift information with respect to a reference image corresponding to a surface of the inspected substrate for each of the plurality of areas, and identifies an inspection area in the three-dimensional image based on an amount of correction calculated based on the plurality of pieces of shift information.
 2. An inspection area identification method for identifying an inspection plane in a three-dimensional image generated from a radiation transmission image of an inspected substrate, the method being characterized by comprising: a step of dividing a tomographic image in the three-dimensional image into a plurality of areas and calculating a piece of shift information with respect to a reference image corresponding to a surface of the inspected substrate for each of the plurality of areas; a step of calculating an amount of correction from the plurality of pieces of shift information; and a step of identifying an inspection area to be inspected in the three-dimensional image based on the amount of correction. 